Link Switch in a Wireless Communication System

ABSTRACT

A wireless device ( 16 ) in a wireless communication system ( 10 ) is configured to perform measurements on a set of candidate links for supporting a network node ( 18 ) in the system ( 10 ) to make a decision as to which of the candidate links is to be a target link for a link switch. The wireless device ( 16 ) reports (e.g., at the physical layer) measured candidate links one link subset at a time in order of the wireless device&#39;s preference for the target link, until the wireless device ( 16 ) receives a target indication signal indicating which of the candidate links in the set is to be the target link. Any given link subset reports one or more candidate links which the wireless device ( 16 ) has measured for the decision. Responsive to receiving the target indication signal, the wireless device ( 16 ) performs the link switch to the indicated target link.

TECHNICAL FIELD

The present application generally relates to a wireless communicationsystem, and more particularly relates to a link switch in a wirelesscommunication system.

BACKGROUND

As channel conditions for a wireless communication device change, thedevice may switch (e.g., handover or reselect) from one wireless link toanother in order to maintain service continuity. The device may forexample switch from accessing the system via one access node, cell,sector, or beam (any of which may serve as a “link”) to accessing thesystem via a different access node, cell, sector, or beam. Towards thisend, when channel conditions on the link via which the device currentlyaccesses the system deteriorates, the system may evaluate which ofdifferent candidate links the device should switch to, if any. Thedevice in this regard may perform measurements on the differentcandidate links and report those measurements to another node in thenetwork (e.g., the serving access node), so that the other node can makethe link switch decision,

Known approaches report such measurements from the device to the networkat the radio resource control (RRC) layer. Reporting measurements atthis relatively high layer enables the device to convey rich, reliablemeasurement information. But RRC layer reporting requires considerablesignaling overhead, heavy radio resource usage, and potentially highlatency. High latency proves especially unattractive where a link switchmust be performed quickly, e.g., before the serving link's qualitydegrades excessively.

SUMMARY

According to one or more embodiments herein, a wireless device reportsmeasured candidate links one link subset at a time, e.g., in order ofthe device's preference for the target link. The device may do so untilthe device receives a signal indicating which candidate link is to bethe target link. Reporting measured candidate links in this way,especially when reported at the physical layer, proves advantageous insome embodiments for realizing a link switch (e.g., handover orreselection) that is fast and lightweight on radio resource usage.

More particular, embodiments herein include a method performed by awireless device in a wireless communication system. The method maycomprise configuring the wireless device to perform measurements on aset of candidate links for supporting a network node in the wirelesscommunication system to make a decision as to which of the candidatelinks is to be a target link for a link switch. The method may alsocomprise reporting measured candidate links one link subset at a time inorder of the wireless device's preference for the target link, until thewireless device receives a target indication signal indicating which ofthe candidate links in the set is to be the target link. Any given linksubset reports one or more candidate links which the wireless device hasmeasured for the decision. This reporting may be performed, for example,at the physical layer. Regardless, the method may further comprise,responsive to receiving the target indication signal, performing thelink switch to the indicated target link.

In some embodiments, this reporting comprises monitoring for receipt ofthe target indication signal during a monitoring interval afterreporting any given link subset, and reporting a subsequent link subsetresponsive to the monitoring interval expiring without receipt of thetarget indication signal.

Alternatively or additionally, such reporting may comprise reporting anygiven link subset, except an initially reported link subset, only afterdetermining that the wireless device did not receive the targetindication signal in response to a previously reported link subset, andrefraining from reporting any more link subsets responsive to receivingthe target indication signal.

In any of these embodiments, reporting may entail (i) ranking measuredcandidate links according to defined ranking criteria at the wirelessdevice that ranks candidate links in descending order of preference forthe target link; (ii) reporting, in a first link subset, one or morecandidate links that are ranked highest according to said ranking; (iii)monitoring for receipt of the target indication signal followingreporting of the first link subset; and (iv) if no target indicationsignal is received during said monitoring, reporting, in a second linksubset, one or more candidate links that are ranked next highestaccording to said ranking.

Embodiments herein also include a performed by a network node in awireless communication system for making a decision as to whichcandidate link in a set of candidate links is to be a target link for alink switch by a wireless device, wherein the wireless device isconfigured to perform measurements on the set of candidate links. Themethod may comprise identifying one or more measured candidate linkswhich the wireless device has reported (e.g., at a physical layer) onelink subset at a time in order of the wireless device's preference forthe target link, wherein any given link subset reports one or morecandidate links in the set which the wireless device has measured forthe decision. The method may also comprise making the decision as towhich identified candidate link is to be the target link, based on theorder in which the wireless device reports candidate links.

In some embodiments, the network node's making of the decision mayentail evaluating whether any given identified candidate link is to bethe target link, further based on one or more characteristics associatedwith that given identified candidate link. In this case, the method mayfurther comprise determining the one or more characteristics using atleast some information not reported by the wireless device. The one ormore characteristics associated with the given identified candidate linkmay include one or more characteristics of the given identifiedcandidate link, one or more characteristics of an access node providingthe given identified candidate link, and/or one or more characteristicsof a backhaul link supporting the given identified candidate link. Inone embodiment, the one or more characteristics include one or more oftraffic load, signaling load, uplink quality, backhaul quality, latency,and usage statistics.

Alternatively or additionally, making the decision may compriseevaluating whether any given identified candidate link is to be thetarget link, further based on one or more of: (i) whether selection ofthe given identified candidate link as the target link would require thewireless device to add another connectivity leg to the system; and (ii)whether selection of the given identified candidate link as the targetlink would require uplink/downlink separation whereby the wirelessdevice connects to different access nodes for uplink and downlinkcommunication.

In some embodiments, any given candidate link is reported by an uplinksignal from the wireless device on that given candidate link. In thiscase, making the decision may comprise evaluating whether a reportedcandidate link is to be the target link by: determining a quality of theuplink signal which reports that candidate link; and evaluating whetherthe reported candidate link is to be the target link, based on thedetermined quality.

In one or more embodiments, the method by the network node may furthercomprise, after the wireless device reports any given link subset:determining whether to make the decision that a reported link candidateis to be the target link; and waiting for report of another link subsetif it is determined not to make the decision.

Alternatively or additionally, the method by the network node mayfurther comprise, responsive to making the decision, controllingtransmission of a target indication signal to the wireless deviceindicating the target link according to the decision made.

In some embodiments, the network node may be a target radio access nodeproviding the target link to the wireless device, such that the methodis performed by that target radio access node. In one such embodiment,the method may further comprise transmitting signaling to a source radioaccess node, which provides a source link to the wireless device,indicating that the target radio access node has made the decision toswitch the wireless device from the source link to the target link.

Alternatively, the method may be performed by a source radio access nodeproviding a source link to the wireless device. In this case, the methodmay further comprise transmitting signaling to a target radio accessnode, which provides the target link to the wireless device, indicatingthe decision made.

In any of these embodiments, identifying one or more measured candidatelinks may comprise receiving signaling from one or more other networknodes that identifies at least one of the one or more measured candidatelinks which the wireless device has reported.

In some embodiments, the method at the network node may further comprisenotifying another network node that provides one of the one or moreidentified candidate links that the decision has been made and/or thatthe wireless device will not report any more candidate links.

In one or more embodiments, the method at the network node furthercomprises, responsive to determining that no identified candidate linkmeets criteria specified as required for the target link, dynamicallyadapting the criteria to be less stringent as needed in order to makethe decision.

In any of the above embodiments, whether at the wireless device or thenetwork node, candidate links that are higher ranked by the wirelessdevice may be reported sooner in time than candidate links that arelower ranked by the wireless device, according to defined rankingcriteria at the wireless device that ranks candidate links in descendingorder of preference for the target link. In some embodiments, thisdefined ranking criteria ranks candidate links that are measured ashaving higher signal quality higher than candidate links that aremeasured as having lower signal quality.

In any of the above embodiments, identities of measured candidate linksand results of the measurements performed on those candidate links maybe reported at the physical layer one link subset at a time.

In any of the above embodiments, only selected ones of the measuredcandidate links that are deemed acceptable by the wireless device as thetarget link, according to one or more defined criteria, may be reportedby the wireless device.

In any of the above embodiments, a confirmation signal may betransmitted by the wireless device towards the network node confirmingreceipt of a target indication signal indicating the target link inaccordance with the decision made.

In any of the above embodiments, a reporting completed signal may betransmitted by the wireless device that indicates the wireless devicewill not report any more measured candidate links for the decision.

In any of the above embodiments, each link subset may report a singlecandidate link which the wireless device has measured for the decision.Alternatively, each link subset may report multiple candidate linkswhich the wireless device has measured for the decision.

In any of the above embodiments, the method may further comprisedynamically configuring how many candidate links are to be reported byeach link subset. This dynamic configuring may occur on a subset bysubset basis in some embodiments.

In any of the above embodiments, any given link subset may be reportedby one or more uplink synchronization signals from the wireless devicethat respectively identify the one or more candidate links in that givenlink subset.

In any of the above embodiments, any given candidate link may bereported by an uplink signal from the wireless device on that givencandidate link.

In any of the above embodiments, any given link subset may be reportedby one or more signals on radio resources that are reserved before thewireless device performs the measurements.

In any of the above embodiments, the target indication signal may betransmitted on a candidate link last used by the wireless device toreport a link subset. Alternatively, the target indication signal may betransmitted on the target link.

In any of the above embodiments, the target indication signal may be anuplink grant and/or a timing advance configuration signal on a physicaldownlink control channel. Alternatively, the target indication signalmay be a reference signal that contains a timing synchronizationcomponent that is common amongst the candidate links and an identitycomponent that identifies the target link.

In any of the above embodiments, the candidate links may be candidatebeams.

Embodiments herein also include corresponding apparatus, computerprograms, carriers, and computer program products.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a wireless communication system thatincludes a wireless device and a network node according to someembodiments.

FIG. 2A is a timing diagram illustrating reporting of candidate linksone link subset at a time according to some embodiments.

FIG. 2B is a timing diagram illustrating reporting of candidate linksone link subset at a time according to other embodiments.

FIG. 3A is a logic flow diagram of processing performed by a wirelessdevice for candidate link reporting according to some embodiments.

FIG. 3B is a logic flow diagram of processing performed by a networknode for making a link switch decision according to some embodiments.

FIG. 4A is a logic flow diagram of processing performed by a wirelessdevice according to some embodiments.

FIG. 4B is a logic flow diagram of processing performed by a networknode according to some embodiments.

FIG. 5A is a block diagram of a wireless device according to someembodiments.

FIG. 5B is a block diagram of a wireless device according to otherembodiments.

FIG. 6A is a block diagram of a network node according to someembodiments,

FIG. 6B is a block diagram of a network node according to otherembodiments.

DETAILED DESCRIPTION

FIG. 1 illustrates a wireless communication system 10 according to oneor more embodiments. As shown, the system 10 (e.g., a 5G system) mayinclude an access network (AN) 12 and a core network (CN) 14. The AN 12wirelessly connects a wireless communication device 16 (or simply“wireless device 16”) to the ON 14. The ON 14 in turn connects thewireless device 16 to one or more external networks (not shown), such asa public switched telephone network and/or a packet data network (e.g.,the Internet).

The AN 12 provides links via which the wireless device 16 may wirelesslyaccess the system 10, e.g., using uplink and/or downlink communications.The AN 12 may for example provide links in the form of access nodes(e.g., base stations), cells, sectors, beams, or the like. Some linksmay provide wireless coverage over different geographical areas.

A network node 18 controls which link the device 16 uses to access thesystem 10. The network node 18 may be in the AN 12 (e.g., in the form ofa base station), or may be in the CN 14 (e.g., in the form of a mobilitymanagement entity, MME). The network node 18 may control which link thedevice 16 uses by for example deciding that the device 16 is to switch(e.g., handover or reselect) from accessing the system 10 via one link(the “source” link) to accessing the system 10 via another link (the“target” link). The network node 18 may choose the target link fromamong a set of multiple links that the network node 18 considers ascandidates for the target link. The device 16 may support the networknode's link switch decision in this regard, such as by reportingmeasured candidate links to the network node 18.

FIG. 1 for instances shows that the network node 18 makes a decision asto which of the candidate links 20A, 20B, and 200 in a set 20 is to bethe target link for a link switch. The network node 18 configures thewireless device 16 to perform measurements on the set 20 of candidatelinks, e.g., to perform measurements of reference signals transmitted onrespective ones of the candidate links. The device 16 correspondinglyreports measured candidate links to the network node 18 for supportingthe network node's link switch decision. The device 16 may for instancereport identities of candidate links that are measured, perhaps alsowith results of the measurements (e.g., in terms of the quality of thereference signals received on respective ones of the candidate links).

Notably, though, the wireless device 16 in FIG. 1 reports measuredcandidate links one “link subset” at a time, with any given link subsetreporting one or more candidate links. Where each link subset reports asingle candidate link, for example, the device 16 may report measuredcandidate links one link at a time. Accordingly, rather than reportingall candidate links in the set 20 during a single reporting instance orwindow, the device 16 may report candidate links one link subset at atime by reporting different portions of those candidate links duringmultiple reporting instances or windows distributed over time, e.g.,within a reporting session defined for the decision. In at least someembodiments described more fully below, the device 16 may reportmeasured candidate links in this way at the physical layer (e.g., bysending candidate link reports as physical layer signals, such as uplinksynchronization signals). Physical layer reporting may for instancefacilitate fast, low-latency link switching that is robust againstsudden serving link loss. Regardless of the layer at which reporting isperformed, by reporting measured candidate links one link subset at atime, the device 16 may effectively delay or defer reporting one or moreof the candidate links in the set on which the device 16 is configuredto measure, e.g., as compared to reporting all candidate links in theset at the same time.

In fact, in some embodiments, the device 16 may delay or defer reportingone or more of the candidate links in the set, in case the network node18 decides in the interim that one of the previously reported candidatelinks is to be the target link. If the network node 18 decides that analready reported candidate link is to be the target link, the device 16may refrain from reporting any additional candidate links in the set,e.g., in order to conserve radio resources.

In one or more embodiments, for example, the wireless device 16 reportsmeasured candidate links one link subset at a time, until the device 16receives a target indication signal (from the network node 18 or anothernode in the system 10) indicating which of the candidate links in theset 20 is to be the target link. Like link reporting, this targetindication signal may also be transmitted at the physical layer in someembodiments. Regardless, responsive to receiving the target indicationsignal, the device 16 may refrain from reporting any more link subsetsand instead perform the link switch to the indicated target link.

In some embodiments, the device 16 may report measured candidate linksone link subset at a time, while monitoring for the target indicationsignal to be received in between or even during report transmissions,e.g., in a frequency duplex division (FDD) mariner. In otherembodiments, the device 16 may report any given link subset (except theinitially reported link subset) only after determining that the device16 did not receive the target indication signal in response to apreviously reported link subset. In this case, the device 16 mayalternate in time between reporting link subsets and monitoring for thetarget indication signal, e.g., such that different link subsets arereported during different, non-consecutive time resources, aridmonitoring is performed during intervening time resources. FIG. 1illustrates one example in this regard.

As shown in FIG. 1, after the wireless device 16 initially transmits afirst report R1 that reports a first link subset 1, the device 16monitors for receipt of the target indication signal during a monitoringinterval M1. The device 16 transmits a second report R2 that reports asecond link subset 2 only responsive to that monitoring interval M1expiring without receipt of the target indication signal. That is, thedevice 16 delays reporting the second link subset 2 until aftermonitoring reveals that the network node 18 did not choose any of thecandidate links in the first link subset 1 to be the target link. Afterreporting the second link subset 2, the device 16 again monitors forreceipt of the target indication signal during a monitoring interval M2.In this example, the device 16 indeed receives the target indicationsignal (TIS) during monitoring interval M2. The device 16 in this caserefrains from reporting any more link subsets, including for example athird link subset 3 that would have been reported after expiration ofthe monitoring interval M2 had the target indication signal not yet beenreceived. Instead, responsive to receiving the target indication signalduring monitoring interval M2, the device 16 may proceed with performingthe link switch to the indicated target link.

In some embodiments, the wireless device 16 reports the candidate linksin a particular order. For example, the wireless device 16 may reportmeasured candidate links one link subset at a time in order of thedevice's preference for the target link. FIG. 1 for instance shows thatthe wireless device 16 organizes the measured candidate links intosubsets 1, 2, and 3, ordered from most preferred to least preferred,e.g., with candidate link 20A most preferred in subset 1, candidate link20B next preferred in subset 2, and candidate link 20C least preferredin subset 3. In this case, then, the wireless device 16 may report morepreferred link subsets sooner in time than reporting lesser preferredlink subsets.

Where a link subset reports multiple candidate links, the device'spreference among the candidate links within that link subset may beindicated in any number of ways, e.g., via multiplexing in the time,frequency, and/or code domain such that individual candidate linkswithin a link subset may be reported consecutively or in parallel withinthe time domain. FIGS. 2A-2B for instances show an example where thedevice 16 reports measured candidate links one link subset at a time byreporting different link subsets 1 and 2 during respective reportingintervals 1 and 2, e.g., with each of those reporting intervals followedby a TIS monitoring interval. A reporting interval may be for instancebetween 1 and 10 subframes, between 1 and 10 ms, or the like, e,g., inorder to give the network node 18 time to process and respond, but alsoavoid switching latency. Within each reporting interval of FIG. 2A, thedevice 16 time multiplexes reporting of the individual candidate linksso as to report more preferred links sooner in time than lesserpreferred links, e.g., Link A is more preferred than Link B and Link Bis more preferred than Link C. Within each reporting interval of FIG.2B, by contrast, the device 16 frequency multiplexes reporting of theindividual candidate links so as to report links according to apredefined convention. The device 16 may for instance report morepreferred links on higher frequencies than lesser preferred links, e.g.,Link A is more preferred than Link B and Link B is more preferred thanLink C.

Regardless of the number of candidate links reported within any givenlink subset, FIG. 3A illustrates processing performed by the wirelessdevice 16 for ordered candidate link reporting according to someembodiments. As shown, the device 16 ranks measured candidate links indescending order of preference for the target link (Block 100). Higherranked measured candidate links are more preferred for the target linkthan lower ranked measured candidate links. This ranking may beperformed according to defined ranking criteria at the device 16, e.g.,that specifies ranking as a function of measured signal quality on thecandidate links such that candidate links measured as having highersignal quality are ranked higher than candidate links measured as havinglower signal quality. In any event, having ranked the measured candidatelinks, the device 16 reports (e,g., at the physical layer) a first linksubset that contains one or more highest ranked candidate links (Block110). Following reporting of the first link subset, the device 16monitors for receipt of the target indication signal (Block 120). If notarget indication is received during that monitoring (NO at Block 130),the device 16 then reports a second link subset that contains one ormore of the next highest ranked candidate links (Block 140). Followingreporting of the second link subset, the device 16 again monitors forreceipt of the target indication signal (Block 120). This process ofalternating between reporting link subsets and monitoring for the targetindication signal may continue until a defined reporting limit isreached (e.g., until the device 16 reports all candidate links in theset 20, or until the device 16 reports selected ones of the candidatelinks which are deemed acceptable by the device 16 as the target link),or until the device 16 receives the target indication signal (whicheveroccurs first). Indeed, once the device 16 receives the target indicationsignal, the device 16 refrains from reporting any further link subsetsand instead performs the link switch to the indicated target link (Block150).

In some embodiments, the device 16 may also transmit a confirmationsignal confirming or acknowledging receipt of the target indicationsignal. This way, the target indication signal may be retransmitted orrepeated if not acknowledged, e.g., within a predefined acknowledgementperiod.

Alternatively or additionally, the device 16 may also transmit areporting completed signal indicating the device 16 will not report anymore measured candidate links for the link switch decision. Thereporting completed signal may prompt the network node 18 to choose thetarget link from among those measured candidate links that have beenreported, e.g., rather than waiting for report of other candidate linksin the set 20 that may not be acceptable to the device as the targetlink.

Irrespective of these possible variations, reporting link subsets inorder of the device's preference for the target link may implicitlyindicate the device's preference for the target link to the network node18. In these and other embodiments, therefore, the network node 18 maymake the decision as to which candidate link is to be the target link,based at least in part on the order in which the device 16 reportscandidate links. The network node 18 may for example apply a biastowards selecting a candidate link reported earlier in time, over acandidate link reported later in time, e.g., so as to preferentiallyselect a candidate link more preferred by the device 16. The networknode 18 in some embodiments may also base its decision on the results ofthe device's measurements on the candidate links, as reported by thedevice 16.

FIG. 3B illustrates processing performed by the network node 18 in thisregard according to some embodiments. As shown, the network node 18receives a report of a link subset (Block 160). Responsive to receipt ofsuch a report, the network node 18 determines whether to make the linkswitch decision at this point, i.e., whether to choose one of thealready reported link candidates to be the target link (Block 170). Ifthe network node 18 decides to not make the decision yet (NO at Block170), the network node 18 waits for the report of another link subset(Block 180). That is, the network node 18 effectively defers the linkswitch decision until one or more additional candidate links arereported, giving the network node 18 more candidate links from which tochoose the target link.

After receiving the report of another link subset (Block 160), thenetwork node 18 may revisit whether to make the link switch decision(Block 170). In some embodiments, the network node 18 may consider onlywhether to choose a candidate link in the last reported link subset. Inother embodiments, though, the network node 178 may consider whether tochoose any previously report candidate link as the target link,including those not reported in the most recent link subset. Inconsidering candidate links reported in different link subsets, thenetwork node 18 may account for the order in which those candidate linkswere reported, e.g., so as to prefer the earlier reported candidate linkover the later reported candidate link. In any event, responsive toeventually making the link switch decision (YES at Block 170), thenetwork node 18 controls the transmission of the target indicationsignal to the wireless device 16 (Block 190). The network node 18 mayfor instance transmit the target indication signal itself, or directthat another node in the system 10 transmit the target indication signalto the device 16. Of course, in some embodiments, the network node 18upon finding no candidate link to be acceptable as the target link mayabort the link switch or restart the measurement procedure with adifferent or expanded set of candidate links as options. Similarly, ifthe device 16 does not receive a target indication signal aftercandidate link reporting completes, the device 16 may maintain itscurrent serving link connection and/or may start the measurement processagain.

Note that the network node 18 in some embodiments may make its linkswitch decision based on one or more other criteria besides the order inwhich the device 16 reports candidate links. For example, the networknode 18 may base its link switch decision on other “network-side”criteria which may not be determinable by or reported by the wirelessdevice 16 alone, e.g., the network-side criteria may be determinableonly upon aggregating reports from multiple devices or may bedeterminable only by network-side measurements. In this way, the linkswitch decision remains network-controlled, rather thandevice-controlled, since the device's link detection and reportingapproach may not be dispositive of which candidate link is chosen as thetarget link. This network-controlled nature of the link switch decisionmay prove advantageous in that it enables the decision to optimizenetwork-wide objectives. Such objectives may include for instance linkload balancing, maximizing overall network capacity, bi-directional linkperformance, or the like.

In one embodiment, for example, the network node's making of thedecision involves evaluating whether any given candidate link is to bethe target link, further based on one or more characteristics associatedwith that link. The one or more characteristics may be associated withthe link in the sense that the one or more characteristics include oneor more characteristics of the candidate link itself, one or morecharacteristics of an access node providing the candidate link, and/orone or more characteristics of a backhaul link supporting the candidatelink. No matter the particular type of characteristic(s), the networknode 18 may determine these one or more characteristics using at leastsome information not reported by the wireless device 16. Thisinformation may for example be reported by one or more other wirelessdevices or one or more other network nodes. Alternatively oradditionally, this information may be determined by the network node 18itself, e.g., in the form of measurements that the network node 18itself performs or in the form of information that the network node 18aggregates from multiple sources. The information in this regard may be“network-side” information that the wireless device 16 itself does nothave visibility into.

For example, one characteristic on which the network node 18 bases itsdecision in some embodiments is load associated with a certain candidatelink. Such load may represent load attributable to traffic (e.g., userdata), signaling, or any combination thereof. And the load may beassociated with the candidate link in the sense that it represents loadon the candidate link itself, load on an access node that provides thecandidate link, load on a backhaul link supporting the candidate link,or any combination thereof. The load associated with a certain candidatelink may be determined by the network node 18 itself responsive to thedevice 16 reporting that candidate link, e.g., as the network node 18has visibility into the traffic and/or signaling associated with thecandidate link for any other devices accessing the system 10 on thatlink. In some embodiments, for example, the network node 18 determinesthe load associated with a link using load information that the networknode 18 measures itself or aggregates from multiple sources (e,g.,multiple devices or network nodes). Such dynamic load determination bythe network node 18 may advantageously account for load changes that mayhave suddenly occurred since link measurements were initiated. In anyevent, the network node 18 may rank each reported candidate link as afunction of the link's reporting order as well as the load associatedwith the link, e.g., with earlier reporting and lighter loads warrantinghigher ranking. The network node 18 may then choose the highest rankedcandidate link, in an effort to choose the earliest reported link withthe load that is the lightest (or at least below a defined loadthreshold).

As one example, the network node 18 may first receive a report of acandidate link associated with a relatively low load. But, rather thanimmediately deciding that the reported candidate link is to be thetarget link, the network node 18 waits to receive report of anothercandidate link, in case another candidate link is associated with aneven lower load. The network node 18 in doing so may prioritize load toa degree over absolutely honoring the device's preference in links, assuggested by the link reporting order. If the network node 18 does notreceive report of another candidate link associated with a lighter load,e.g., within a certain reporting window, the network node 18 in someembodiments may then choose the earlier reported candidate link as thetarget link.

In other embodiments, the network node 18 may simply choose the earliestreported candidate link associated with a load that is below a definedthreshold. In this case, the network node 18 prioritizes the device'spreference in links over load, as the network node 18 would not “fish”for links associated with lighter loads at the expense of upsetting thedevice's preference for the target link.

Although the one or more characteristics that the network node 18 maybase its decision on were exemplified with load as one possiblecharacteristic, the one or more characteristics may alternatively oradditionally include other types of characteristics associated with alink. Other types of characteristics in this regard may include one ormore of: uplink quality, backhaul quality, latency, usage statistics,uplink/downlink separation requirements, and multi-connectivityrequirements. In one specific example, for instance, the network node 18may choose the target link from among reported candidate links, in orderto realize a particular tradeoff between the device's preference for thetarget link (as represented by the link reporting order), loadassociated with the links, and latency associated with the links.

As another specific example in the context of multi-connectivity, thenetwork node 18 may evaluate whether any given candidate link is to bethe target link, based on the link's reporting order and further basedon whether selection of that link as the target link would require thedevice 16 to add another connectivity leg to the system 10. Forinstance, the network node 18 may prefer selection of a candidate linkthat would not require the addition of another connectively leg (e.g.,connectivity to another access node), over selection of a candidate linkthat would require such addition.

As a further example in the context of uplink/downlink separation, thenetwork node 18 may evaluate whether any given candidate link is to bethe target link, based on the link's reporting order and further basedon whether selection of that link as the target link would requireuplink/downlink separation, whereby the device 16 connects to differentaccess nodes for uplink and downlink communication (i.e., one accessnode for downlink and a different access node for uplink). For instance,where the link switch only concerns the switching of the link used foreither uplink or downlink, not both, the network node 18 may preferselection of a candidate link that would not require uplink/downlinkseparation, over a candidate link that would require such separation.

As yet another example, the network node 18 may choose the target linkfrom among reported candidate links, in order to realize a particulartradeoff between the device's preference for the target link (asrepresented by the link reporting order) and measured uplink qualityassociated with the links. In one embodiment, for instance, any givencandidate link may be reported by an uplink signal from the device 16 onthat candidate link, e.g., such that the device 16 reports differentcandidate links with uplink signals transmitted on those respectivecandidate links. In this case, the quality of the respective uplinksignals may be measured, e.g., by one or more networks nodes thatrespectively receive those uplink signals. Accordingly, the network node18 may evaluate whether a reported candidate link is to be the targetlink by determining the quality of the uplink signal which reports thatcandidate link and evaluating whether the link is to be the target linkbased on that determined quality (as well as the link's reportingorder). Where the device forms its preference for the target link basedon measured downlink quality associated with the links, such an approachthat accounts for uplink quality associated with the links may aim toselect a target link with the best bi-directional (.e., uplink anddownlink) performance,

In these and other embodiments where the network node 16 attempts toidentify and select a target link that meets one or more specifiedcriteria (e.g., a specified load level, a specified uplink qualitythreshold, etc.), scenarios may occur where none of the reportedcandidate links meet that criteria. In some embodiments, this may meanthat the network node 16 does not make the link switch decision. Inother embodiments, though, the network node 16 may dynamically adapt theone or more criteria to be less stringent, as needed in order to makethe link switch decision. This dynamic adaptation of the selectioncriteria may for instance enable a “softer” tradeoff between the aspectsimpacting the target link selection. For example, if none of thecandidate links are associated with loads below a defined load thresholdand/or uplink qualities above a defined quality threshold, the networknode 16 may dynamically adapt one or more of those thresholds, e.g., asneeded to select the “least bad” candidate link.

Alternatively or additionally, the number of candidate links to bereported by each link subset may be dynamically adapted or configured,e.g., based on any of the above-described characteristics or othercharacteristics. That is, although in some embodiments the number ofcandidate links reported in each link subset is statically defined(e.g., to be one or a predefined number greater than one), in otherembodiments that number is dynamically adapted. The network node 18 mayindicate the number of candidate links to be reported in a link subsetwhen configuring the device 16 to perform the measurements.

Such dynamic adaptation may be made on a decision-wide basis so as toapply to all reported link subsets. In one embodiment, for example, thedevice 16 receives a single indicator that indicates how many links areto be reported in each link subset. In another embodiment, the device 16may receive an indicator for each candidate link indicating whetherreporting for that candidate link may be bundled with one or more othercandidate links in a single link subset, but only reports multiple linksin each subset if all candidate links permit it; otherwise, the device16 reports a single link in each subset. In still other embodiments, thedynamic adaptation may be made on a subset by subset basis, such thatdifferent subsets may report different numbers of links. For example,the device 16 may alternate between single link reporting and multi-linkreporting during the same measurement procedure. The device 16 may forinstance report a.

single link in a first subset, await for a TIS, and then report multiplelinks in a second subset, e.g., if report bundling is permitted forthose links,

Regardless, dynamic adaptation may be based upon for instance any of theabove-described characteristics associated with a candidate link and/orany network deployment characteristics or operating status. In oneembodiment, for instance, the network node 18 dynamically configures thenumber of candidate links in a link subset to be one when the networknode 18 detects high backhaul latency and low loads. And the networknode 18 dynamically configures the number of candidate links in a linksubset to be a number greater than one when the network node 18 detectshigh downlink traffic loads, e.g., in order to better facilitate loadbalancing. In general, though, the more candidate links reported in alink subset, the greater the number of radio resources consumed and thegreater the risk that radio resources may be wasted.

Of course, as alluded to above, link reporting may be performed in someembodiments at the physical layer, meaning that radio resourceconsumption may be leaner anyways as compared to higher-layer (e.g., RRClayer) reporting with higher overhead. Reporting at the physical layermay be realized using any type of physical signal or message. A physicalsignal or message may for instance convey a predefined sequence thatmaps to a link identity or convey coded data that carries a linkidentity. In one embodiment, for example, any given link subset isreported by one or more uplink synchronization signals (USSs) from thewireless device 16 that respectively identify the one or more candidatelinks in that given link subset. A USS may for instance be a locallyunique signal which carries a synchronization pilot and an identity of acandidate link.

Link reporting may also convey measurement results at the physical layerin a similar manner. A physical signal or message may for instanceconvey a predefined sequence that maps to a measurement result value orconvey coded data that carries a measurement result value.

No matter the particular type of physical signal used for reporting,though, any given candidate link in some embodiments is reported by oneor more signals on radio resources that are reserved before the wirelessdevice 16 performs the measurements. That is, resources for linkreporting may be reserved ahead of time, which may enable reporting tobe conveyed with minimal latency.

Alternatively or additionally, the target indication signal used in someembodiments above may be transmitted at the physical layer using anytype of physical signal. In one embodiment, for example, the targetindication signal is an uplink grant and/or a timing advanceconfiguration signal, e.g., on a downlink control channel such as aphysical downlink control channel (PDCCH). In this case, the wirelessdevice 16 may detect the target indication signal using downlinksynchronization obtained during the measurement phase. In anotherembodiment, by contrast, the target indication signal is a specialreference signal dedicated to indicating the target link, i.e., a targetindication reference signal. The reference signal may for instancecontain a timing synchronization component that is common amongst thecandidate links and an identity component that identifies the targetlink. The timing synchronization component may even provide the downlinksynchronization of the target link. In one embodiment, the targetindication signal is the same (repeated) reference signal as that whichthe device 16 measured on the target link for reporting. In anotherembodiment, the target indication signal may be a single sequence usedno matter which candidate link is selected as the target link.

Different embodiments herein envision that link reporting may beperformed over different possible links, as may target indication. Inone embodiment, for example, the device 16 reports any given candidatelink using an uplink signal transmitted on that given candidate link, orreports any given link subset using an uplink signal transmitted on oneof the candidate links included in that link subset. In anotherembodiment, by contrast, the device 16 may report a given candidate linkby transmitting an uplink signal over a different candidate link, e.g.,the current serving link. Likewise, in one embodiment, the targetindication signal may be transmitted on the indicated target link. Thismay advantageously improve the robustness of link switching to suddenquality loss on the source link. In another embodiment, by contrast, thetarget indication signal may be transmitted on the candidate link lastused by the device 16 to report a link subset.

The link over which reporting and target indication is transported, andother factors, may implicate different nodes in the system 10 in thelink switch decision. For example, in some embodiments where the device16 reports any given candidate link using an uplink signal transmittedon that given candidate link, the access node providing that candidatelink may itself make a local, independent decision as to whether thereported candidate link is to be the target link. That is, even thoughthe device 16 may report candidate links to different access nodes ifthose links are in fact provided by multiple access nodes, nointer-access node coordination may be needed, since each access node mayindependently assess whether one or more of the candidate links itprovides meets selection criteria specified for the target link. Anaccess node that receives report of a candidate link which meets theselection criteria may simply select that link as the target. The accessnode may do so irrespective of whether any other candidate linksprovided by other access nodes may better meet that selection criteria,at least in embodiments where ordered link reporting by the device 16one subset at a time suggests that the device 16 prefers the earliestreported link which meets the selection criteria. In these embodimentswhere each access node providing a candidate link independently assesseswhether that candidate link is to be the target link, each of thoseaccess nodes may therefore independently operate as the network node 18in FIG. 1.

In some embodiments such as this where different access nodes may makeindependent link switch decisions in their role as network node 18, thedevice may report just one candidate link at a time. Limiting the linksubset size to one in this way may preclude multiple access nodes thatprovide different candidate links from each independently selecting adifferent candidate link as the target link, resulting in a target linkconflict or race condition. This way, only one access node (e.g., thetarget access node) will ultimately make the link switch decision. Theonly sort of inter-node coordination that may take place may involvenotifying the source access node that the serving access node haschanged. For example, the network node 18 may transmit signaling to thesource access node indicating that the decision has been made to switchthe wireless device 16 from the source link to the target link. Thetarget access node may also retrieve the device's context (e.g., packetdata protocol context) from the source access node, unless it has beentransferred proactively prior to the switch.

Correspondingly, in other embodiments where the device 16 may report acandidate link subset that includes more than one candidate link,inter-node coordination may be required when different access nodesprovide different reported candidate links in the same subset. Forexample, in some embodiments, the network node 18 operates as a central,controlling, or coordinating node that receives signaling from one ormore other network nodes identifying at least one of the one or moremeasured candidate links which the wireless device 16 has reported,e.g., so as to centrally collect the device's link reports. In someembodiments, the network node 18 may receive signaling indicatingcandidate link reporting in the same order as that with which the device16 reports it, e.g., any intermediate nodes forward candidate linkreporting immediately or promptly on to the network node 18. Regardless,the network node 18 may then transmit signaling to one or more accessnodes, including for instance the target access node, indicating thedecision made. At least one of those access nodes may then in turn sendthe target indication signal to the device 16. The network node 18 inthese embodiments may be for instance the source or serving access node.

Embodiments such as this where the network node 18 operates as acontrolling node provide an architecture conducive to adaptive selectioncriteria as described above. For example, any access node that receivescandidate link reporting from the device 16 may forward or otherwisenotify the network node 18 of that reporting. If the network node'sevaluation of the reporting suggests that no candidate link meets thecurrent selection criteria for the target link, the network node 18 maydynamically adapt the criteria to be less stringent, as needed in orderto make the decision.

A variation of these adaptive selection criteria embodiments employs ahierarchical or distributed decision architecture. In this variation, alink switch decision may be made either locally (i.e., independently) byan access node that provides a candidate link, or centrally by acontrolling node if no access node makes the decision locally. If anaccess node makes the link switch decision locally, for example, theaccess node may inform the controlling node of the decision, eitherbefore or after transmitting the target indication signal to the device16. If the controlling node is not informed of a decision by any accessnode, the controlling node makes the decision based on candidate linkreporting that the controlling node proactively or reactively collectsfrom the access nodes involved. The collected candidate link reportingmay still indicate the device's reporting order, e.g., via the order inwhich the controlling node receives that reporting or via timestampedreceipt by the access nodes. The controlling node may also make thedecision based on information obtained regarding other criteria orcharacteristics discussed above. The controlling node may then informthe access node that controls the selected target link, whereupon thataccess node transmits the target indication signal to the device 16.

In any embodiment where an access node may receive candidate linkreporting from the device 16, but the link switch decision may be madeelsewhere, the access node may be informed when the decision is madeand/or that the device 16 will not report any more candidate links. Thisway, rather than the access node continuing to monitor for additionalcandidate link reporting from the device 16 (at least until a definedmaximum reporting session duration), the access node may cease thatmonitoring when no longer needed. The monitored radio resources may thenbe used for other communications, so as to conserve capacity. In oneembodiment, for example, the controlling node (e.g., source access node)or the target access node informs all non-selected access nodes thatcandidate link reporting is finished. In another embodiment, the device16 transmits “end of reporting” signaling either before or after itreceives the target indication signal. This end of reporting signalingmay be for instance an uplink synchronization signal which has asequence dedicated or configured to indicate the device 16 has finishedcandidate link reporting.

In general, therefore, a network node 18 herein may be any node in theAN 12 or CN 14 that evaluates whether a reported candidate link is to bethe target link. In at least some embodiments where such evaluation maybe performed by more than one node, there may be more than one nodefunctioning as a network node 18. For example, a network node 18 may bethe source access node, the target access node, a core network node, orany controlling node (e.g., C-RAN). A network node 18 may receive linkreporting directly from the device 16 to support its link switchdecision, or may receive link reporting indirectly from one or moreaccess nodes. And a network node 18 may transmit the target indicationsignal directly to the device 18, or may direct an access node (e.g.,the target access node) to transmit the target indication signal to thedevice 18.

Different embodiments may therefore involve the wireless device 16transmitting candidate link reporting to different nodes and/ormonitoring for a target indication signal from different nodes. Forinstance, in some embodiments, the device 16 reports a candidate linkusing an uplink signal transmitted on that candidate link, whereas inother embodiments the device 16 may report a candidate link using anuplink signal transmitted on a different candidate link (e.g., theserving link). And, in some embodiments, the device 16 monitors for thetarget indication signal only on the candidate link that the device 16last used for candidate link reporting, whereas in other embodiments thedevice 16 monitors for the target indication signal on a predefined oneof the candidate links (e,g., the source link). In these instances wherethe device 16 knows the link on which a target indication signal may bereceived, the device 16 may use the time and frequency synchronizationassociated with that candidate link (e.g., associated with reception ofthe reference signal measured on that candidate link). In otherembodiments, though, the device 16 may receive the target indicationsignal on any of the candidate links, meaning that the device 16 maymonitor more than one candidate link (e,g., all links) for the targetindication signal. In fact, in some embodiments, the device 16 mayattempt to receive the target indication signal on any reported linkusing blind detection, e.g., by limiting its time and frequencysynchronization to the synchronization used to receive the referencesignal measured on that candidate link. Alternatively or additionally,where the target indication signal is a target indication referencesignal (e.g., target indication mobility reference signal, TI-MRS), theTIS configuration may define the TI-MRS search space in terms oftime-frequency resources and sequences for detection and/or may definethe mapping of the target link to the transmitted target indicationreference signal.

Note that embodiments herein are applicable to any type of wirelesscommunication system (e.g., Long Term Evolution, Wideband CDMA, GSM,Wifi or the like) for switching between links of any kind (e.g., cells,sectors, nodes, beams). In one embodiment, for instance, the system 10is a cell-based system in which cell-specific reference signals (CRS)are broadcasted in all cells in an always-on, static manner for mobilitymeasurements. In this case, the wireless device 16 may periodicallymeasure links in the form of cells using the CRS and may report thosemeasurements when certain reporting conditions are met (periodic orevent based).

In another embodiment, the wireless communication system is a 5G systemthat employs high-gain beamforming and that transmits mobility referencesignals (MRS) on respective beams in a dynamic manner for mobilitymeasurements, i.e., MRS are turned on when needed. Each activated beammay transmit a (device-specific) MRS that contains a timingsynchronization component (TSS) whose contents may be common to allbeams and a beam identity component (BRS) that is beam-specific. In thiscase, the wireless device 16 may measure links in the form of beamsusing MRS that are transmitted on those respective beams. The networkmay configure the device 16 to measure certain candidate beams usingrespectively configured MRS, e.g., namely those that are most likely tobe acceptable. However, not all candidate beams and MRS configured mayend up being acceptable, e.g., due to sudden load changes since mobilitymeasurements are initiated or due to the network transmitting some ofthe MRS also for purposes of automatic neighbor relation (ANR)establishment. Furthermore, the network may have activated beams whichare not optimally directed towards the device 16, e.g., especially ifthe beams are narrow and feedback from the device 16 has not yet beenreceived. Hence, multiple redundant MRS transmitting beams may beactivated for mobility measurements.

Especially in embodiments wherein links are beams realized with highradio frequencies (e.g., microwave) and high-gain beamforming, linkswitching approaches described herein advantageously providelightweight, fast (on average), low latency switching, the importance ofwhich is emphasized by the poor diffraction and penetration propertiesof the high radio frequencies. Indeed, the switching approach hereinproves effective in completing the switch even in the face of a rapidlydeteriorating source beam. Moreover, the prolonged reporting approachherein, such as where the device 16 reports the best detected candidatebeams in a sequential manner using USS, enables the network to considerfactors other than beam quality in its switch decision (e.g., beamload).

A network node herein is any type of node in the wireless communicationsystem 10, e,g., in the access network 12 or core network 14. A radionode herein is any type of node (e,g., a base station or wirelesscommunication device) capable of communicating with another node overradio signals. A radio network node is any type of radio node within theaccess network 12, such as a base station. A wireless communicationdevice or simply wireless device is any type of radio node capable ofcommunicating with a radio network node or another wirelesscommunication device over radio signals. A wireless communication devicemay therefore refer to a machine-to-machine (M2M) device, a machine-typecommunications (MTC) device, a narrowband internet of things (NB-IoT)device, etc. The wireless device may also be a user equipment (UE),however it should be noted that the UE does not necessarily have a“user” in the sense of an individual person owning and/or operating thedevice. A wireless device may also be referred to as a radio device, aradio communication device, a wireless terminal, or simply aterminal—unless the context indicates otherwise, the use of any of theseterms is intended to include device-to-device UEs or devices,machine-type devices or devices capable of machine-to-machinecommunication, sensors equipped with a wireless device, wireless-enabledtable computers, mobile terminals, smart phones, laptop-embeddedequipped (LEE), laptop-mounted equipment (LME), USB dongles, wirelesscustomer-premises equipment (CPE), etc. In the discussion herein, theterms machine-to-machine (M2M) device, machine-type communication (MTC)device, wireless sensor, and sensor may also be used. It should beunderstood that these devices may be UEs, but are generally configuredto transmit and/or receive data without direct human interaction.

In an IOT scenario, a wireless communication device as described hereinmay be, or may be comprised in, a machine or device that performsmonitoring or measurements, and transmits the results of such monitoringmeasurements to another device or a network. Particular examples of suchmachines are power meters, industrial machinery, or home or personalappliances, e.g. refrigerators, televisions, personal wearables such aswatches etc. In other scenarios, a wireless communication device asdescribed herein may be comprised in a vehicle and may performmonitoring and/or reporting of the vehicle's operational status or otherfunctions associated with the vehicle.

In view of the above modifications and variations, FIGS. 4A and 4Bgenerally indicate processing performed by a wireless device 16 and anetwork node 18, respectively, according to some embodiments. As shownin FIG. 4A, processing by the wireless device 16 includes configuringthe device 16 to perform measurements on a set 20 of candidate links forsupporting a network node 18 in the system 10 to make a decision as towhich of the candidate links is to be a target link for a link switch(Block 100). Processing by the wireless device 16 further includesreporting (e.g., at the physical layer) measured candidate links onelink subset at a time in order of the wireless device's preference forthe target link, until the wireless device 16 receives a targetindication signal indicating which of the candidate links in the set 20is to be the target link (Block 110). Any given link subset reports oneor more candidate links which the wireless device has measured for thedecision. Processing by the wireless device 16 also includes, responsiveto receiving the target indication signal, performing the link switch tothe indicated target link (Block 120).

As shown in FIG. 4B, processing by the network node 18 includesidentifying one or more measured candidate links which the wirelessdevice 16 has reported (e.g., at the physical layer) one link subset ata time in order of the device's preference for the target link (Block200). Again, any given link subset reports one or more candidate linkswhich the wireless device has measured for the decision. Processing bythe network node 18 also includes making the decision as to whichidentified candidate link is to be the target link, based on the orderin which the device 16 reports candidate links (Block 210).

Note that a wireless device 16 as described above may perform the methodin FIG. 4A and any other processing herein by implementing anyfunctional means or units. In one embodiment, for example, the wirelessdevice 16 comprises respective circuits or circuitry configured toperform the steps shown in FIG. 4A. The circuits or circuitry in thisregard may comprise circuits dedicated to performing certain functionalprocessing and/or one or more microprocessors in conjunction withmemory. In embodiments that employ memory, which may comprise one orseveral types of memory such as read-only memory (ROM), random-accessmemory, cache memory, flash memory devices, optical storage devices,etc., the memory stores program code that, when executed by the one ormore processors, carries out the techniques described herein.

FIG. 5A for example illustrates the wireless device 16 in accordancewith one or more embodiments. As shown, the wireless device 16 includesprocessing circuitry 300 and communication circuitry 310. Thecommunication circuitry 310 (e.g., in the form of a transmitter,receiver, transceiver, or radio frequency circuitry) is configured totransmit and/or receive information to and/or from one or more othernodes, e.g., via any communication technology. Such communication mayoccur via one or more antennas that are either internal or external tothe wireless device 16 as shown. The processing circuitry 300 isconfigured to perform processing described above, e.g., in FIG. 4A, suchas by executing instructions stored in memory 320. The processingcircuitry 300 in this regard may implement certain functional means,units, or modules.

FIG. 5B illustrates the wireless device 16 in accordance with one ormore other embodiments. As shown, wireless device 16 implements variousfunctional means, units, or modules, e.g., via the processing circuitry300 in FIG. 5A and/or via software code, for implementing thefunctionality described above (e.g., for implementing the steps in FIG.4A). These functional means, units, or modules include for instance aconfiguring module or unit 340 for configuring the wireless device 16 toperform measurements on the set of candidate links, a reporting moduleor unit 350 for (e.g., at the physical layer) reporting measuredcandidate links one link subset at a time, and a link switch module orunit 360 for performing the link switch to the target link, as describedabove.

Also note that a network node 18 as described above may perform themethod in FIG. 4B, and any other processing herein, by implementing anyfunctional means or units. In one embodiment, for example, the networknode 18 comprises respective circuits or circuitry configured to performthe steps shown in FIG. 4B. The circuits or circuitry in this regard maycomprise circuits dedicated to performing certain functional processingand/or one or more microprocessors in conjunction with memory. Inembodiments that employ memory, which may comprise one or several typesof memory such as read-only memory (ROM), random-access memory, cachememory, flash memory devices, optical storage devices, etc., the memorystores program code that, when executed by the one or more processors,carries out the techniques described herein.

FIG. 6A illustrates the network node 18 in accordance with one or moreembodiments.

As shown, the network node 18 includes processing circuitry 400 andcommunication circuitry 410. The communication circuitry 410 (e,g., inthe form of a transmitter, receiver, transceiver, or radio frequencycircuitry) is configured to transmit and/or receive information toand/or from one or more other nodes, e.g., via any communicationtechnology. Where the network node 18 is an access node (e.g., a basestation), such communication may occur via one or more antennas that areeither internal or external to the network node 18, as shown. Theprocessing circuitry 400 is configured to perform processing describedabove, e.g., in FIG. 4B, such as by executing instructions stored inmemory 420. The processing circuitry 400 in this regard may implementcertain functional means, units, or modules.

FIG. 6B illustrates the network node 18 in accordance with one or moreother embodiments. As shown, the network node 18 implements variousfunctional means, units, or modules, e.g., via the processing circuitry400 in FIG. 6A and/or via software code, e.g., for performing respectivesteps in FIG. 4B. These functional means, units, or modules include forinstance an identifying module or unit 430 for identifying one or moremeasured candidate links which the wireless device 16 has reported(e.g., at the physical layer) one link subset at a time in order of thewireless device's preference for the target link. Also included may be adecision module or unit 440 for making the decision as to whichidentified candidate link is to be the target link, based on the orderin which the wireless device reports candidate links.

Those skilled in the art will also appreciate that embodiments hereinfurther include corresponding computer programs,

A computer program comprises instructions which, when executed on atleast one processor of a node (e,g., network node 18 or wireless device16), cause the node to carry out any of the respective processingdescribed above. A computer program in this regard may comprise one ormore code modules corresponding to the means or units described above.

Embodiments further include a carrier containing such a computerprogram. This carrier may comprise one of an electronic signal, opticalsignal, radio signal, or computer readable storage medium.

In this regard, embodiments herein also include a computer programproduct stored on a non-transitory computer readable (storage orrecording) medium and comprising instructions that, when executed by aprocessor of a node, cause the node to perform as described above.

Embodiments further include a computer program product comprisingprogram code portions for performing the steps of any of the embodimentsherein when the computer program product is executed by a computingdevice. This computer program product may be stored on a computerreadable recording medium.

Note that the term “subset” is used herein in its general sense to referto a part or portion of a larger set. This contrasts with themathematical or technical sense of the term in which a subset may be thesame as the set. In mathematical terms, a “subset” as used herein isreally a “proper subset.” Accordingly, a “link subset” as used hereinrefers to a part or portion of the larger set of candidate links onwhich the wireless device 16 is configured to perform measurements.

The present invention may, of course, be carried out in other ways thanthose specifically set forth herein without departing from essentialcharacteristics of the invention. The present embodiments are to beconsidered in all respects as illustrative and not restrictive, and allchanges coming within the meaning and equivalency range of the appendedclaims are intended to be embraced therein.

1-42. (canceled)
 43. A method performed by a wireless device in awireless communication system, the method comprising: configuring thewireless device to perform measurements on a set of candidate links forsupporting a network node in the wireless communication system to make adecision as to which of the candidate links is to be a target link for alink switch; at a physical layer, reporting measured candidate links onelink subset at a time in order of the wireless device's preference forthe target link, until the wireless device receives a target indicationsignal indicating which of the candidate links in the set is to be thetarget link, wherein any given link subset reports one or more candidatelinks which the wireless device has measured for the decision; andresponsive to receiving the target indication signal, performing thelink switch to the indicated target link.
 44. The method of claim 43,wherein said reporting comprises: monitoring for receipt of the targetindication signal during a monitoring interval after reporting any givenlink subset; and reporting a subsequent link subset responsive to themonitoring interval expiring without receipt of the target indicationsignal.
 45. The method of claim 43, wherein said reporting comprisesreporting any given link subset, except an initially reported linksubset, only after determining that the wireless device did not receivethe target indication signal in response to a previously reported linksubset, and refraining from reporting any more link subsets responsiveto receiving the target indication signal.
 46. The method of claim 43,wherein said reporting comprises: ranking measured candidate linksaccording to defined ranking criteria at the wireless device that rankscandidate links in descending order of preference for the target link;reporting, in a first link subset, one or more candidate links that areranked highest according to said ranking; monitoring for receipt of thetarget indication signal following reporting of the first link subset;and if no target indication signal is received during said monitoring,reporting, in a second link subset, one or more candidate links that areranked next highest according to said ranking.
 47. The method of claim46, wherein the defined ranking criteria ranks candidate links that aremeasured as having higher signal quality higher than candidate linksthat are measured as having lower signal quality.
 48. The method ofclaim 43, wherein identities of measured candidate links and results ofthe measurements performed on those candidate links are reported at thephysical layer one link subset at a time.
 49. The method of claim 43,wherein only selected ones of the measured candidate links that aredeemed acceptable by the wireless device as the target link, accordingto one or more defined criteria, are reported by the wireless device.50. The method of claim 43, wherein each link subset reports a singlecandidate link which the wireless device has measured for the decision.51. The method of claim 43, wherein each link subset reports multiplecandidate links which the wireless device has measured for the decision.52. The method of claim 43, further comprising dynamically configuringhow many candidate links are to be reported by each link subset.
 53. Themethod of claim 43, wherein any given link subset is reported by one ormore uplink synchronization signals from the wireless device thatrespectively identify the one or more candidate links in that given linksubset.
 54. The method of claim 43, wherein any given candidate link isreported by an uplink signal from the wireless device on that givencandidate link.
 55. The method of claim 43, wherein any given linksubset is reported by one or more signals on radio resources that arereserved before the wireless device performs the measurements.
 56. Themethod of claim 43, wherein the target indication signal is transmittedon the target link.
 57. The method of claim 43, wherein the targetindication signal is an uplink grant and/or a timing advanceconfiguration signal on a physical downlink control channel.
 58. Themethod of claim 43, wherein the target indication signal is a referencesignal that contains a timing synchronization component that is commonamongst the candidate links and an identity component that identifiesthe target link.
 59. The method of claim 43, wherein the candidate linksare candidate beams.
 60. A method performed by a network node in awireless communication system for making a decision as to whichcandidate link in a set of candidate links is to be a target link for alink switch by a wireless device, wherein the wireless device isconfigured to perform measurements on the set of candidate links, themethod comprising: identifying one or more measured candidate linkswhich the wireless device has reported at a physical layer one linksubset at a time in order of the wireless device's preference for thetarget link, wherein any given link subset reports one or more candidatelinks in the set which the wireless device has measured for thedecision; and making the decision as to which identified candidate linkis to be the target link, based on the order in which the wirelessdevice reports candidate links.
 61. The method of claim 60, whereinmaking the decision comprises evaluating whether any given identifiedcandidate link is to be the target link, further based on one or morecharacteristics associated with that given identified candidate link,and wherein the method further comprises determining the one or morecharacteristics using at least some information not reported by thewireless device.
 62. The method of claim 61, wherein the one or morecharacteristics include one or more of traffic load, signaling load,uplink quality, backhaul quality, latency, and usage statistics.
 63. Themethod of claim 61, wherein the one or more characteristics associatedwith the given identified candidate link include one or morecharacteristics of the given identified candidate link, one or morecharacteristics of an access node providing the given identifiedcandidate link, and/or one or more characteristics of a backhaul linksupporting the given identified candidate link.
 64. The method of claim60, wherein making the decision comprises evaluating whether any givenidentified candidate link is to be the target link, further based on oneor more of: whether selection of the given identified candidate link asthe target link would require the wireless device to add anotherconnectivity leg to the system; and whether selection of the givenidentified candidate link as the target link would requireuplink/downlink separation whereby the wireless device connects todifferent access nodes for uplink and downlink communication.
 65. Themethod of claim 60, wherein any given candidate link is reported by anuplink signal from the wireless device on that given candidate link, andwherein making the decision comprises evaluating whether a reportedcandidate link is to be the target link by: determining a quality of theuplink signal which reports that candidate link; and evaluating whetherthe reported candidate link is to be the target link, based on thedetermined quality.
 66. The method of claim 60, further comprising,after the wireless device reports any given link subset: determiningwhether to make the decision that a reported link candidate is to be thetarget link; and waiting for report of another link subset if it isdetermined not to make the decision.
 67. The method of claim 60, furthercomprising, responsive to making the decision, controlling transmissionof a target indication signal to the wireless device indicating thetarget link according to the decision made.
 68. The method of claim 60,wherein the method is performed by a target radio access node providingthe target link to the wireless device.
 69. The method of claim 60,further comprising, responsive to determining that no identifiedcandidate link meets criteria specified as required for the target link,dynamically adapting the criteria to be less stringent as needed inorder to make the decision.
 70. The method of claim 60, whereincandidate links that are higher ranked by the wireless device arereported sooner in time than candidate links that are lower ranked bythe wireless device, according to defined ranking criteria at thewireless device that ranks candidate links in descending order ofpreference for the target link.
 71. A wireless device for use in awireless communication system, the wireless device comprising:processing circuitry and a memory, the memory containing instructionsexecutable by the processing circuitry whereby the wireless device isconfigured to: configure the wireless device to perform measurements ona set of candidate links for supporting a network node in the wirelesscommunication system to make a decision as to which of the candidatelinks is to be a target link for a link switch; at a physical layer,report measured candidate links one link subset at a time in order ofthe wireless device's preference for the target link, until the wirelessdevice receives a target indication signal indicating which of thecandidate links in the set is to be the target link, wherein any givenlink subset reports one or more candidate links which the wirelessdevice has measured for the decision; and responsive to receiving thetarget indication signal, perform the link switch to the indicatedtarget link.
 72. A network node for use in a wireless communicationsystem for making a decision as to which candidate link in a set ofcandidate links is to be a target link for a link switch by a wirelessdevice, wherein the wireless device is configured to performmeasurements on the set of candidate links, the network node comprising:processing circuitry and a memory, the memory containing instructionsexecutable by the processing circuitry whereby the network node isconfigured to: identify one or more measured candidate links which thewireless device has reported at a physical layer one link subset at atime in order of the wireless device's preference for the target link,wherein any given link subset reports one or more candidate links in theset which the wireless device has measured for the decision; and makethe decision as to which identified candidate link is to be the targetlink, based on the order in which the wireless device reports candidatelinks.